I'm running into a weird issues in which a Firebase query using orderByChild() doesn't actually order the data. Below is a snapshot of the data that I'm trying to order: (total is off for the sake of this example)
This is the code that I've used so far:
Query query = locationComment.orderByKey();
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.getValue() == null) {
return;
}
data.clear();
adapter.notifyDataSetChanged();
String userId;
String time;
String comment;
Map<String, String> commentMap = (Map) dataSnapshot.getValue();
for (Map.Entry<String, String> entry : commentMap.entrySet()) {
if(!((entry.getKey()).contains("total"))) {
String[] keyString = (entry.getKey()).split(",");
time = keyString[0];
userId = keyString[1];
comment = entry.getValue();
Date resultdate = new Date(Integer.parseInt(time));
data.add(new Comment(comment,
DateFormat.getDateTimeInstance().format(resultdate), userId));
adapter.notifyItemInserted(data.size());
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
I'm getting each and every key-value pair (barring total) except that it's not in order as expected (ordered by key). The Firebase docs say that the keys are ordered lexicographically if they can't be parsed into a 32 bit integer.
Either way though the order should be as shown in the image but the data that I get back while looping through the map is not in this order.
I would really appreciate it if someone could point me in the right direction. Thanks!
When you execute a query you get three things:
they keys
the values
the relative order between these
When you convert the result to a Map it can only hold two of these, so the order is lost. To prevent this, you should use the DataSnapshot.getChildren() method:
Query query = locationComment.orderByKey();
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.getValue() == null) {
return;
}
data.clear();
for (DataSnapshot child : dataSnapshot.getChildren()) {
...
}
adapter.notifyDataSetChanged();
}
Also see this example in the Firebase documentation on working with lists: https://firebase.google.com/docs/database/android/lists-of-data#listen_for_value_events
Looks like your data is badly structured.
Firebase has it's internal way of keying, and Firebase only can order those keys, with additional criteria if wanted. But since your key, is a custom key, firebase can't and won't order this branch.
The solution is to restructure your data in a meaningful way, like this
+ comments
+ total: 13
+ data:
+ 12uoasjihdou3
+ time: xx
+ userID: xx
+ comment: xx
+ 123tjiueoi134
+ 1piahf9hasheui
+ 6890324890oiuwer
Always use push() to generate new keys, do not create custom keys for lists, thats a total no go
FirebaseDatabase.getReference("comments").child("data").push({yourdata});
if you want to order your data, this is how you do that
FirebaseDatabase.getReference("comments").child("data").orderByChild("time");
Related
I have a database something like this. How I want to compare the value for all users to get most value.
restaurant
-userUid
-stateUid
-restaurantUid
-price = 9
-restaurantUid2
-price = 10
-stateUid2
-restaurantUid3
-price = 2
As you can see the database there, stateUid price is 19 while stateUid2 price is only 2
So, stateUid has the most price. How to compare them and display the most one. Thank you
EDIT:
I have done something like this, and it's error at return. And the value is not working.
exports.calculateTotal = functions.database.ref('/restaurant/{userUid}/{stateUid}/{restaurantUid}')
.onWrite((change, context) => {
// Only edit data when it is first created.
if (change.before.exists()) {
return null;
}
// Exit when the data is deleted.
if (!change.after.exists()) {
return null;
}
//Get id
const restaurantUid = context.params.restaurantUid;
let totalValue = 0;
change.after.forEach(function (item) {
totalValue += item.child('total').val();
});
console.log(totalValue);
return functions.database.ref('/priceTotal/' + restaurantUid).child('total').set(totalValue);
});
Firebase queries work on a flat list of nodes. A query can contain only a single unknown key, the key of the direct child nodes under the location where you query. In your data structure there are multiple levels of unknown keys, which means that you can't query for the highest price across all of them.
What you can do in your current data structure is query across one state for the restaurant with the highest price. That'd look something like:
DatabaseReference ref = FirebaseDatabase.getInstance().getReference("restaurant");
DatabaseReference stateRef = ref.child("userUid").child("stateId");
stateRef.orderByChild("price").limitToLast(1).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot snapshot: dataSnapshot.getChildren()) {
Log.i(TAG, snapshot.getKey()+": "+snapshot.child("price").getValue(Long.class));
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
}
But you can't search across all states for a user, or even all users. If you want to allow that, you'll have to store all prices in a flat list, like:
restaurant_prices: {
"restaurantid": {
price: 9,
state: "statid",
user: "userid"
}
}
Also see:
Firebase Query Double Nested
Firebase query if child of child contains a value
int totalPrice = 0;
int greaterPrice = 0;
int temp = 0;
DatabaseRefernce restRef = FirebaseDatabase.getInstance().getReference().child("restaurant").child(userUid);
restRef.addValueEventListener(new ValueEventListener(){
onDataChange(Datasnapshot snapshot) {
for(Datasnapshot snap : snapshot) {
String key = snap.getKey();
//This will return you the keys of stateUid
restRef.child(key).addValueEventListener(new ValueEventListener(){
onDataChanged(DatSnapshot datasnapshot) {
//this for loop will iterate through restaurants of that specific state
for(DataSnapshot snap2 : datasnapshot){
totalPrice += (int) snap2..child("price").getValue();
}
//When this loop ends you will get the total price of all restaurants from that state
}
});
//as u see above I mentioned greater price and temp variable
using simple logic of finding greatest number out of two number save the value of greatest integer to the variable every time you loop through state
}
}
}
);
Use nested for loops to iterate from database like above and calculate your prices
Else what you can do is when you are uploading the data of restos - while uploading prices just make an extra node for total price of city and add price of resto every time you upload new resto
I'm trying to develop a simple application to learn firebase database.
Here is my realtime database schema
mydirectory
-contact_list
-LOyDhepB_IZlM6lZtko
mobileNumber: "9385746982"
name: "Jay"
-LOyDhetiPHalLhXrOaU
mobileNumber: "8000478912"
name: "Ravi"
-LOyDhetiPHalLhXrOaV
mobileNumber: "123456789"
name: "ABC"
-LOyDheubruATyyBp8dG
mobileNumber: "023456879"
name: "XYZ"
I want to get the list of data ordered by name
So I'm using this snippet to load the data in my android application
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
mDatabase.child("contact_list").orderByChild("name").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Map<String, Object> objectMap = (HashMap<String, Object>) dataSnapshot.getValue();
Master.personList.clear();
for (Object obj : objectMap.values()) {
if (obj instanceof Map) {
Map<String, Object> mapObj = (Map<String, Object>) obj;
String name = (String) mapObj.get("name");
String mobileNumber = (String) mapObj.get("mobileNumber");
Person person = new Person(name, mobileNumber);
Master.personList.add(person);
populateListView();
}
}
}
#Override
public void onCancelled(DatabaseError error) {
// Failed to read value
Log.w("ANDs", "Failed to read value.", error.toException());
}
});
But it does not sort data based on the alphabetical order of name
key. Am I doing anything wrong or missing something?
P.S.
I've also indexing rules (ref), but still result is same! It doesn't sort data alphabetical wise.
{
"rules": {
"mydirectory": {
"contact_list": {
"$user_id": {
".indexOn": ["name"]
}
}
},
".read": true,
".write": true
}
}
I've tried many things from other posts like this topic but nothing works! Please don't make it duplicate instead please help me to solve it!
A HashMap can only contain a key and a value. And the keys in a Map are by definition not ordered. So when you call dataSnapshot.getValue(), you're throwing away all ordering information.
To maintain the order, you'll need to loop over dataSnapshot.getChildren():
public void onDataChange(DataSnapshot dataSnapshot) {
Master.personList.clear();
for (DataSnapshot contactSnapshot: dataSnapshot.getChildren()) {
String name = contactSnapshot.child("name").getValue(String.class);
String mobileNumber = contactSnapshot.child("mobileNumber").getValue(String.class);
Person person = new Person(name, mobileNumber);
Master.personList.add(person);
}
populateListView();
}
You'll also notice that I use child(...) to get a child snapshot for a specific property and get the String value from it. Your approach for that would work too, but I find that I get better error messages when I stick to a snapshot longer (instead of converting to a Map).
String userID = selectedCharacter.getUserID();
String charID = selectedCharacter.getCharID();
Character editedCharacter = new Character(userID, charID, name, hitPoints, armorClass, level, experience, gold);
databaseRef
.orderByChild("charID")
.equalTo(selectedCharacter.getCharID())
.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// Translate the character to a map of its data
Map<String,Object> updates = editedCharacter.toMap();
// Update ONLY the node with charID = editedCharacter.getCharID()
databaseRef.updateChildren(updates);
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
});
So I'm trying to update a character's stats in my firebase database. As you can see:
here
the code I'm using is actually putting the update in character's root instead. What am I doing wrong here? I'm unsure of how to find the node with the key as I'm not storing the key anywhere.
When you execute a query against the Firebase Database, there will potentially be multiple results. So the snapshot contains a list of those results. Even if there is only a single result, the snapshot will contain a list of one result.
So your code will need to handle the fact that the snapshot is a list. In the case of Android that means that you loop over snapshot.getChildren():
databaseRef
.orderByChild("charID")
.equalTo(selectedCharacter.getCharID())
.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot child: dataSnapshot.getChildren()) {
// Translate the character to a map of its data
Map<String,Object> updates = editedCharacter.toMap();
// Update ONLY the node with charID = editedCharacter.getCharID()
child.getRef().updateChildren(updates);
}
}
Instead of databaseRef.updateChildren(updates);
Could you try
databaseRef.child(dataSnapshot.getKey()).setValue(updates)
Then see if it works.
I have data structure as:
https://law-apps-44h221543638e.firebaseio.com/apps to promote/0/ >> name:"First App", package:"fra"
https://law-apps-44h221543638e.firebaseio.com/apps to promote/1/ >> name:"Second App", package:"sca"
https://law-apps-44h221543638e.firebaseio.com/apps to promote/2/ >> name:"Third App", package:"tha"
and I query it using
Firebase myFirebaseReference = new Firebase("https://law-apps-44h221543638e.firebaseio.com/apps to promote");
Query queryRef = myFirebaseReference.orderByChild("name");
queryRef.addListenerForSingleValueEvent(new ValueEventListener() { // override methods })
But it returns the data in the same order i.e sorted by the first child (1,2,3, etc.)
How should I query it so it sorts the data by the "name" tag of each child?
Ok so I found the answer to this question and I am writing it so others may benefit from it. I was using an older technique wherein I was finding from datasnapshot my apps using their parents' numbers and due to this, I was delibrately undoing the ordering.
Now I have used dataSnapshot.getChildren().iterator() and it is now working correctly. Here's the code:
Query queryRef = myFirebaseReference.orderByChild("name");
queryRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String name;
String my_package;
long lengthOfForLoop = dataSnapshot.getChildrenCount();
Iterator<DataSnapshot> child = dataSnapshot.getChildren().iterator();
for (int i = 0; i < lengthOfForLoop; i++) {
DataSnapshot next = child.next();
name = next.child("name").getValue(String.class);
my_package = next.child("package").getValue(String.class);
// do something with this data.
}
}
});
}
thanks, Usman!
I used the same code with the children iterable collection in a for loop.
This code was worked for me (in Kotlin):
accountsReference.child(accountId).child("actions").orderByChild("actionPosition").addListenerForSingleValueEvent( object : ValueEventListener {
override fun onDataChange(var1: DataSnapshot) {
if (var1.children != null) {
for (actionsEntries in var1.children) {
...
}
}
I am having some issues with the Android version of my app. I completed the iOS version and am working on the Android data part. After I get the the snapshot in Swift, I can simply say something like this:
myList.addObject((snapshot.value["num"] as? String)!)
Then I have a nice list of of the numbers I need.
So far with Android it isn't that simple. Here is my how my data is structured and what I am looking for.
staffNUM
--staff
--12345677
-- num:112234
--2345689
-- num:090909
--44445677
-- num:999234
--6665689
-- num:888673
I can't change the way the data is created since the app for iOS is already being used.
Here is the question:
I have a reference to my database, which works.
mDatabase = FirebaseDatabase.getInstance().getReference();
Here is how I am calling the database after:
mDatabase.child("staffNUM/staff").addListenerForSingleValueEvent(
new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.getValue() != null) {
Log.d("Snap", "" + dataSnapshot.getValue());
StaffNum staffNum = dataSnapshot.getValue(StaffNum.class);
} else {
// something else happens
}
My results in the snapshot are:
D/Snap: {staff={12345677={num=112234},{2345689 ={num= 090909},{2345689 ={num= 090909}, {44445677={num= 999234}, {6665689 ={num= 888673}}
What is the best way to parse that data? I just need a list like I did in Swift to use in the app.
Edit:
Here is the class I added
#IgnoreExtraProperties
public class StaffNum {
public String num
public StaffNUM() {}
public StaffNUM(String num) {
this.num = num;
}
#Exclude
public Map<String, Object> toMap() {
HashMap<String, Object> result = new HashMap<>();
result.put("num", num);
return results;
}
}
If I call Log.d("num: ","" + staffNUM.num);
I still get
D/num:: null
Create a Staff POJO with the fields that you need from your Firebase structure
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot d : dataSnapshot.getChildren()) {
Staff staff = d.getValue(Staff.class);
Log.d("Snap", "num: " + staff.getNum());
}
}